1. Field of the Invention
This invention relates to a pad provided in a videotape cassette (hereinafter referred to simply as "pad"), and more particularly to a cylindrical pad equipped with a frictionless and wear-free member at a part of the pad which will contact a videotape when provided in the interior of a videotape cassette
2. Description of the Prior Art
Videotape recorders for amateur use which are capable of recording and/or reproducing video and audio signals have been developed and put into mass-production. (The word, "videotape recording-and-reproducing apparatus" hereinafter used denotes a videotape recording-and-reproducing apparatus and an apparatus designed exclusively for recording or for reproducing only.) When videotape recording-and-reproducing apparatuses first appeared, open-reel type videotapes were commonly used. Disadvantageously, these videotapes are difficult to handle, and they require a relatively large space to mount in a videotape recording-and-reproducing apparatus. In an attempt to solve these and other problems which prevent reduction of the size of a videotape recording-and-reproducing apparatus, a lighter and smaller videotape cassette and a videotape recording-and-reproducing apparatus provided with facilities for mounting such videotape cassette were developed and manufactured.
As is well known, video signals are recorded or reproduced magnetically along a magnetic tape as the magnetic tape travels across a recording or reproducing head with a coating of powdered magnetic material of the tape in contact with the head. In the recording the videotape is magnetized in accordance with the video and audio signals impressed thereon, whereas in the reproducing the video and audio signals are magnetically retrieved in the form of electrical signals. As is well known, in the case of recording audio signals alone, it suffices that a recording tape is magnetized along its length in accordance with audio signals impressed thereon.
Video signals, however, contain much more information than audio signals, and, therefore, it is impractical for an ordinary recording tape to store video information if such information is stored as magnetic signals along the length of the tape. In an attempt to increase the density at which information is stored on an ordinary magnetic recording tape to the extent that the tape can record as much information as contained in video signals, the tape is magnetized obliquely to its length with the aid of a rotating multiple head which scans obliquely across the width of the tape at a speed greater than the normal travel speed of the tape in the longitudinal direction.
Any irregularity in speed or "jitter" in the longitudinal direction of travel of the tape will adversely affect the recording and reproducing of the video signals, so the quality of recorded or reproduced video signals depends on the stability of the longitudinal speed of a videotape.
Usually a videotape recording-and-reproducing apparatus is equipped with a servo control for maintaining a videotape at a constant speed in the longitudinal direction, thereby assuring that video signals are recorded and reproduced with high fidelity.
In abnormal running conditions, however, undesired external factors are liable to affect the travel of a videotape. In some instances sudden changes in tractive force arising from irregular movements of reels causes the moving videotape to deviate from its regular path of travel which is defined by guide members. As a result the videotape cannot maintain its travel at a given constant speed.
In an attempt to prevent a moving videotape from deviating from its regular path of travel under the influence of such undesirable forces acting on the videotape, a pad has been provided in the interior of the videotape cassette.
To allow a recording and/or reproducing head to get ready an access to and contact with a videotape which is contained in a videotape cassette, a part of the videotape extending between the pay-out and the take-up reels in the cassette is exposed to the exterior of the cassette. This arrangement requires providing a pad in the interior of a cassette for the purpose of preventing the videotape from becoming loose and coming out of the cassette when the cassette is not fitted in a videotape recording-and-reproducing apparatus.
FIG. 1 shows a perspective view of a part of a videotape cassette equipped with a conventional pad. As shown, the pad 10 consists of a base plate 1 and a substantially frictionless portion 2 applied to a free end of the base plate 1, which is adapted to contact with a videotape in the interior of the cassette. The other end of the base plate 1 is fixed to a stationary stand 8. With this arrangement the pad 10 pushes the videotape 5 against an associated guide stud 7.
FIG. 2A is a front view of a conventional pad, and FIG. 2B is a plane view of the pad of FIG. 2A.
As seen in these figures, the pad consists of a resilient base plate 1 and a substantially frictionless strip portion 2 affixed to one end of the base plate with a piece of adhesive tape 3.
In the arrangement seen in FIG. 1, and with reference to FIGS. 2A and 2B, the base plate 1 is fixed to a stationary stand 8 along an end 1a, and is yieldingly bent with its frictionless strip 2 pushing a videotape 5 against the guide surface of the guide stud 7. This arrangement naturally requires a substantial extension of the base plate in the dimension from end 1a to end 1b, and accordingly a conventional pad requires the provision of a relatively large space in the interior of a small-sized videotape cassette. Thus, provision of such a pad in the interior of a videotape cassette obstructs extensive reduction of the size of the cassette. The base plate 1 is fixed along its end 1a to a stationary stand 8 with adhesive. This requires much care and accordingly, lowers the efficiency of fabrication, making it difficult to mass-produce videotape cassettes.